Electroluminescent Driver
In place of an internal, on-chip oscillator, the driver uses an external 32kHz clock signal to drive control signals for both coil and lamp circuitry. This feature reduces die size and product cost while providing a means for precision control over coil and lamp frequencies, as well as tight performance over wide temperature extremes. The 32kHz operation is synchronized with standard clock designs in single-cell applications.
The driver is a high-voltage output DC-AC inverter specifically designed to drive electroluminescent lamps to backlight liquid crystal displays, keypads, and readouts used in battery-operated portable equipment. It operates from a +2.2V to +4.5V battery source and features a low-power standby mode that draws less than 100nA (typical) standby current. SP4414 is offered in 8-pin SOIC and 8-pin µSOIC packages and is capable of providing high-drive capability for EL lamps up to 4 square inches in size.
The use of an external 32kHz clock simplifies the backlight system design by eliminating the need to select external resistor values and models in order to set internal oscillator frequencies. Removal of the on-chip oscillator also enables precision control of coil and lamp frequencies over a wide temperature range (-40° C to 85° C). In addition, a total of only three external components are required for standard operation (1 inductor, 1 capacitor, and 1 optional fast-recovery diode), minimizing overall board space and system cost.
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